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Need help buying memory question about voltage

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a b } Memory
July 23, 2010 9:34:54 PM

Hey guys I was thinking about adding some new memory for my 3 year old computer. The memory I currently have looks like this.

Information SPD EEPROM (DIMM_A1) :
Manufacturer : Corsair
Part Number : CM2X1024-6400
Serial Number : Unspecified
Type : DDR2-SDRAM PC2-6400 (399 MHz) - [DDR2-800]
Format : Regular UDIMM (133.35 x 3)
Size : 1024 MB (2 ranks, 4 banks)
Module Buffered : No
Module Registered : No
Module SLi Ready (EPP) : No
Width : 64-bit
Error Correction Capability (EC... No
Max. Burst Length : 8
Refresh : Reduced (.5x)7.8, Self Refreshµs
Voltage : SSTL 1.8v
Prefetch Buffer : 4-bit
Manufacture : Week 23 of 2006
Supported Frequencies : 270 MHz, 400 MHz
CAS Latency (tCL) : 4 clocks @ 270 MHz, 5 clocks @ 400 MHz
RAS to CAS (tRCD) : 4 clocks @ 270 MHz, 5 clocks @ 400 MHz
RAS Precharge (tRP) : 4 clocks @ 270 MHz, 5 clocks @ 400 MHz
Cycle Time (tRAS) : 13 clocks @ 270 MHz, 18 clocks @ 400 MHz
Min TRC : 15 clocks @ 270 MHz, 22 clocks @ 400 MHz

I'm looking to get 4 gigs total. I'm thinking about getting 2 sticks of 1 GB and I think DDR2 Ram works best in multiples of 2 so 4 sticks total would work. Does it matter if RAM is from a different manufacturer, or the voltage is different and does CAS latency or timing, do those have to be similar.

Thanks for your help in advance.
a b } Memory
July 24, 2010 7:26:58 PM

Quote:
Hey guys I was thinking about adding some new memory for my 3 year old computer. The memory I currently have looks like this.

Information SPD EEPROM (DIMM_A1) :
Manufacturer : Corsair
Part Number : CM2X1024-6400
Serial Number : Unspecified
Type : DDR2-SDRAM PC2-6400 (399 MHz) - [DDR2-800]
Format : Regular UDIMM (133.35 x 3)
Size : 1024 MB (2 ranks, 4 banks)
Module Buffered : No
Module Registered : No
Module SLi Ready (EPP) : No
Width : 64-bit
Error Correction Capability (EC... No
Max. Burst Length : 8
Refresh : Reduced (.5x)7.8, Self Refreshµs
Voltage : SSTL 1.8v
Prefetch Buffer : 4-bit
Manufacture : Week 23 of 2006
Supported Frequencies : 270 MHz, 400 MHz
CAS Latency (tCL) : 4 clocks @ 270 MHz, 5 clocks @ 400 MHz
RAS to CAS (tRCD) : 4 clocks @ 270 MHz, 5 clocks @ 400 MHz
RAS Precharge (tRP) : 4 clocks @ 270 MHz, 5 clocks @ 400 MHz
Cycle Time (tRAS) : 13 clocks @ 270 MHz, 18 clocks @ 400 MHz
Min TRC : 15 clocks @ 270 MHz, 22 clocks @ 400 MHz

I'm looking to get 4 gigs total. I'm thinking about getting 2 sticks of 1 GB and I think DDR2 Ram works best in multiples of 2 so 4 sticks total would work. Does it matter if RAM is from a different manufacturer, or the voltage is different and does CAS latency or timing, do those have to be similar. Yes, it matters. Get RAM with the same voltage and latencies. You would be better off getting two new sticks of 2 GB RAM sold as a set. This will help avoid problems when the BIOS tries to read and set the RAM SPD.

Thanks for your help in advance.

above^
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July 24, 2010 10:19:44 PM

Agree with Iam. I would take it further and suggest getting two new sticks that are the same, or as close to the same as possible, as the old memory. This will minimze stability issues.

As you may already know, if you get any faster memory it will be tuned down to run at the same speed as the old (slowest) memory.
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a c 104 } Memory
July 25, 2010 1:49:12 AM

Some motherboards are very sensitive to mismatched ram. Even ram from the same vendor with the same part number can be made with different manufacturing technology. That is why ram is sold in kits.
The ram at least has to be of the same voltage, and type. It will operate at the lowest common denominator of performance.

With Corsair, you have a decent chance of being OK if you buy another kit just like what you have.

If you want to be very safe, get a full 4gb kit of 2 x 2gb and sell the old ram on e-bay.
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July 25, 2010 2:55:21 AM

Yes, all very good advice here.
The DDR2 spec is 1.8V but 2.0V works better. Most 'secretary' type motherboards cannot deliver that.
It used to be a bit of a problem. If you were unaware you could get voltage incompatibilities...
DDR3 works so much better, runs 1.5V solid, crazy speeds too! runs great.
To the OP:
2GB memory is the practical maximum for 32-bit OS, especially with 1GB or 2GB vidcard.
If you want more, you go 64-bit OS.
If you go 64-bit OS, forget 4GB, you get 8GB RAM.
(Triple-channel guys are lucky, we can go 6GB for cheap, heheh...)
But forget 4GB! :)  Go 2GB or 8GB depending on OS.
Anyway, to answer your question specifically:
Special high-perf DDR2 can require big voltage, sometimes 2.1V minimum.
That Corsair you have is great, because it will always POST at a nice low default 1.8V, not all DDR2 will.
But it can still overclock with big voltage and everything fine, offering the best of both worlds...
Mobos can become confused by mismatched channels and/or SPDs.
But the newest chipsets now say you can do it! 2 x 512MB on one channel, and a single 1GB stick on the other... kewl.
Anyway you could pound 4 x 1GB in there, WTF give it a try, 2 x 1GB DDR2 is still affordably cheap.
If I wanted more than 2GB, personally, I would buy 2 x 2GB chips, and run 6GB with a 64-bit OS.
So the 64-bit OS actually becomes more important to me than new RAM at that point.
But you, couldn't you just install 2 x 512MB? You're only going to get 3GB max anyway...
Regards
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a b } Memory
July 25, 2010 3:11:04 AM

Adding more modules affects the memory bus load.

If you're currently running your two modules with a Command Per Clock or Command Rate of 1T (or 1N) you may have to run the four modules at a Command Per Clock or Command Rate of 2T (or 2N).
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July 29, 2010 12:06:44 AM

The_OGS said:
2GB memory is the practical maximum for 32-bit OS, especially with 1GB or 2GB vidcard.

No. I have a 32-bit OS with 4 x 1 GB of memory. While the OS cannot see all of it because of memory address limits, it does see 3.2 GB which provides substantially more speed than only 2 GB. Your could add 2 x 500 MB for a total of 3.0 GB in your system - my old system had this - but I choose to go with 4 x 1 GB to keep all the memory the same rather than using the less expensive 500 MB memory. I don't know how much the performance difference is, but I decided to invest the small additional cost to provide the extra memory and benefit - if any - of stability.

The_OGS said:
If you want more, you go 64-bit OS. If you go 64-bit OS, forget 4GB, you get 8GB RAM.

Why? A THG analysis of about 6 to 8 months ago proved that few applications and no games used more than 3 GB of memory. That may have increased a little sense then and may increase further as programs better use multiple threads. If I were building now, I would be inclided to go for the 8 GB as I don't have significant budget issues. But others might, and might benefit from getting less memory to invest more in the graphics card right now. Or simply might now be able to afford the 8 GB that might have little if any impact on current performance.
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a c 104 } Memory
July 29, 2010 12:59:42 AM

Few applications will use more than 2gb, and certainly 3gb as rockyjohn said. It takes special coding to use more, photoshop CS4 is an example.

If you ran only one task such as a game, then 4gb would be a practical size.

If you are doing a lot of multitasking, then more than 4gb is useful to keep those other tasks from interfering with each other and getting paged in and out.

XP was built when ram was expensive, so it does lots of paging trying to keep ram available.

Vista and Windows7 can use lots of ram. They keep things around in anticipation or reuse. They may even predict what you will use and try to load it into ram before you ask for it. So with the more modern OS'es 6gb , 8gb, or even more might be appropriate.

3gb is better than 2gb. 3.3gb(about what a 32 bit OS can see) is 10% better than 3gb.
Here is a corsair study on the value of 4gb vs. 2gb for games:
http://www.corsair.com/_appnotes/AN804_Gaming_Performan...
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